Printed circuit boards are joined together in order to form a larger board. Joining printed circuit boards may be advantageous, for example, to join because different printed circuit boards, manufactured by different manufacturers and serving different functions. Additionally, printed circuit board size is limited, and by joining together printed circuit boards, larger boards may be formed.
One prior art method of joining printed circuit boards is using stamped metal leads. Stamped metal leads are soldered to traces on one of the printed circuit boards to be joined together. These stamped metal leads provide the spring force needed to establish electrical contact. A standard connection may require up to 50 grams (g) of force on each metal lead. For a 64 metal lead printed circuit board, this would be 50 g * 64=3200 g=3.2 kg=7.04 pounds. Therefore, the stamped metal leads have to provide sufficient spring force to provide such pressure. Typically, stamped metal contacts increase metal lead length in order to provide the required spring force. When the daughter board is coupled to the mother board, the metal contacts are first wiped, and then coupled together. Generally the stamped metal contacts are soldered. In this way a secure connection is established.
This method has numerous disadvantages. Usually the boards can only be attached end to end. The connection is not easily disconnected. The initial wiping required makes these boards not field replaceable. Gold leads are expensive, but are used because other metals do not provide sufficient spring force. The length of the stamped metal contacts is determined by the spring force needed. Since the metal contacts provide the spring force, the impedance and inductance of the spring metal contacts is not controlled.